Green energy sources like wind and wave power are to account for 40% of Scotland's electricity by 2020, environment minister Ross Finnie has announced.

At present, about 11% of Scotland's electricity comes from renewable sources - hydropower alone accounts for 10%.

A target of 18% of electricity by 2010 had originally been set by the Scottish Executive.

But ministers are confident that this will be achieved because dozens of wind power projects are already in the pipeline and that prompted the setting of the more ambitious long-term target of 40%.

Ross Finnie launched a period of consultation

Mr Finnie said: "Scotland's capacity for generating electricity from renewable resources is one of the largest in Europe, amounting to a staggering 75% of the entire UK installed generating capacity.

"If we are serious about tackling climate change then we have to exploit this resource to the full."

He added: "I firmly believe that producing as much as 40% of Scotland's electricity from renewable sources by 2020 is a realistic aim."

The minister said big utility firms had already announced investment plans exceeding �1bn for renewable energy projects over the next decade and more were in the pipeline.

"I know that the market is there and set to increase, representing a great potential for Scottish manufacturing and jobs."

He hailed the 40% commitment, which the executive describes as "aspirational objective" rather than a formal target, as a serious commitment to helping reduce greenhouse gases.

Scotland's coastline offers a source of wave power

The consultation paper launched on Friday by the executive is taking place at the same time as a UK-wide consultation on energy policy.

The executive denied the new 40% target will lead to the countryside being covered in wind farms.

Mr Finnie argued that other promising forms of renewable energy, like wave and tidal power, were in their early stages but offered huge potential.

"My aim is that Scotland should be a world leader in the field of renewable energy - all forms of renewable energy," he said.